Apparatus for testing cable elements



March 2l\ 1950 D. M. TAGGART APPARATUS FR TESTING CABLE ELEMENTS FiledDec. 3, 1946 Patented Mar. 21, 1950 APPARATUS FOR TESTING CABLE ELEMENTSDawson M. Taggart, Ruxton, Md., assigner to Western Electric Company,Incorporated, New York, N. Y., a corporation of New York ApplicationDecember 3, 1946, Serial No. 713,641

(Cl. 21S- 11) 3 Claims.

This invention relates to apparatus for testing cable elements, and moreparticularly to apparatus for testing elements forming parts of coaxialcable units.

Coaxial cables are widely used in long distance telephone transmissionlines and usually consist of a plurality of individual coaxial unitstwisted together to form a composite core which is enclosed in a leadsheath. Each of the coaxial units consists of a solid central conductor,an outer tubular conductor formed therearound and spaced concentrictherewith by disc-shaped insulators spacedly positioned on the centralconductor and a steel tape spirally wrapped around the outer conductor.

It was found that the transmission characteristics of the coaxial unitsare vitally affected by the presence of conductive faults within thecoaxial unit which provides a path of reduced dielectric strengthbetween the central and outer conductors. These faults may take manyforms, the more common being a microscopic conductive lm of dirt on theinsulating discs, bits of metal embedded in the discs, or very iinemetallic slivers or splinters attached to the' central conductor.

In the manufacture of such coaxial units, a solid conductor iscontinuously advanced through a coaxial unit forming machine, whichfirst applies the insulator discs thereon in uniform spaced relation toform a coaxial unit core. The central conductor with the discs attachedis advanced through a high potential electrode for the purpose ofelectrically burning away any conductive faults that may be present inthe conductor and disc assembly and then through a high potentialtesting electrode to ascertain whether or not any faults remain. If nofaults are detected by the testing electrode the outer tubular conductoris formed over the discs by a subsequent operation of the formingmachine. i

The types of electrodes used heretofore for burning out faults in andtesting the conditions oi such a conductor and disc assemblage areprovided with a substantially circular passage designed to slidablyengage the peripheries of the discs positioned on the advancingconductor. It was discovered that the central conductor and discassembly did not travel in a fixed path between the disc applyingapparatus and the outer conductor forming apparatus of the coaxialforming machine, but varied slightly in all directions. This variationin the travel of the conductor caused the discs to engage portions ofthe circular passage through which they were advanced with such forcethat sometimes the discs were displaced on the central conductor.

ln addition, the passage through this type of electrode must beelliptical in cross section in order that slightly oversize insulatingldiscs may be advanced therethrough without being displaced on thecentral conductor. Consequently, the average insulating disc contactsthe elliptical passage at the top and bottom only, which means that anyfault which happens to be located outside oi the direct line between thepoint of contact between the disc and the electrode and the groundedcentral conductor may not be removed by the burn-out electrode.

In order to overcome the disadvantages present in the types ofelectrodes known heretofore, it is desirable that an electrode beprovided in which no relative movement occurs between the contactingmembers and the insulating discs of the core, and the contactiingmembers engage the entire periphery of the discs.

An object of the invention is to provide new and improved apparatus fortesting cable elements, and more particularly to provide simple andeffective apparatus for testing elements of coaxial units.

In accordance with a specific embodiment of the invention, there isprovided an electrode for impressing a high potential across acontinuously advancing coaxial unit core which comprises a pair ofendless chains driven. in timed relation with the advancing core unitand arranged to carry a plurality of disc contacting members. The chainsare synchronized with each other so that their respective electrodescome together at a predetermined point and completely engage a disc onthe advancing core and move in unison with the advancing core so that norelative movement occurs between the contacting members and the discs ofthe core unit. a

A clear understanding of the invention may be had Jfrom the followingdetailed description oi a specic embodiment thereof, when read inconjunction with the appended drawing, in which:

Fig. l a diagrammatic side view of a coaxial unit forming machineshowing testing electrodes embodying the invention;

Fig. 2 is an enlarged, plan View of one' ofthe electrcdes shown in Fig.l;

Fig. 3 is a vertical, sectional view taken along line 3--3 of Fig. 2,and

Fig. 4 is an enlarged, plan View of a portion of the apparatus shown inFigs. 2 and 3.

Referring now to the drawing and more particularly to Fig. 1, a coaxialunit forming machine, indicated generally by the numeral IS, has acapstan 1I associated therewith which serves to advance a conductor l2from a suitable supply source (not shown) through a disc applyingapparatus `,I3,`of a suitable design, by the aid of which insulatingdiscs ifi-I4 are positioned on the conductor I2 at uniformly spaceintervals to form a coaxial unit core I5. As the core I5 is continuouslyadvanced from the disc applying apparatus I3, it is engaged by aburn-out electrode It, a testing electrode I1 and then passes through atube forming die i8 which forms a copper tape 2G vdrawn from a supplypad 2| longitudinally around the discs Iii-I4 of the core I5 for form atubular conductor 22. The partially formed coaxial unit advances througha taping head 23, of knowndesign, by means of which a plurality oi steeltapes are servedis'pirally around the conductor 22 to form a completedcoaxial unit 24, which, after passing, around the capstan II severaltimes, is diu 4rected to suitable takeup means (not shown).

The burn-out electrode I6 is connected to one side of a high potentialburn-out circuit ener- "fgized and controlled by suitable electricalapparatus indicated generally at by a conductor The. testing electrodeI1 is connected to one side "of a hignpotential testing circuit alsoenergized aridcontrolled by the electrical apparatus indicated generallyat`25 by a conductor 21 (Fig. l).

The oppositev side of the burn-out circuit and the testing circuit areconnected to ground, and the A"conductor lI2 is connected to ground at28 which "arrangement serves to apply a high burn-out orAtesting'potential across the portion of the core ISen'g'a'ged bytheelectrodes I 6 and i1, respec-1 tively. The purpose of the'burn-outelectrode l 5 "is to electrically burn' away or vaporize any corductivefault which might be present in the core I5, andthe purpose of thetesting electrode Il is to test the lcore I5" after it has been treatedby 'the testingv electrode I5 to ascertain whether any conductive faultsremain in the core.

The electrical apparatus indicated generally at 25 is as 4sociated withthe testing electrode I1 in such a "manner that, should' any fault bepresent in the `portion of the core I5 being engaged by the test- `ingelectrode I1, the driving means (not shown) for the entire coaxialforming machine lli is den energized thereby preventing the tubular con-'ductor 22 'from being formed around a defective core.

It is believed to be Iapparent that the capstan `I I, the' discapplyingapparatus I3 and the taping head 23 must be driven in timedrelation with ref y,spect toy each other in order to form a uniform`4coaxial unit 24. Therefore, when a defect in the core `I5 is'noteliminated by the testing electrode I6, an electrical circuit is formedtherethrough by means ofthe testing electrode I1 which serves todeenergize'all thedriven elements of the coaxial `unit`macliine IU'simultaneously. For a complete description and disclosure of theelectrical ciru cuit and apparatus associated with the burn-outrespectively, are identical in construction and operation and for thatreason only the burn-out '3U (Fig. 2).

vided in the arms '4d-M,

electrode I6 will be described in detail hereinbelow.

Referring now to Fig. 3, it will be noted that the electrode I6comprises a rectangular base 30 oi' suitable electrical insulatingmaterial and having a bore 3l provided adjacent to each corner thereor`for receiving a self-lubricating bushing 32. Each of thebushings'32-'32iis provided with a hanged head which serves to maintainthe bushings in proper position in the bore 3l provided in the .base 3U.A shaft 33 is provided with a reduced body portion 34, which isrotatably positioned in the bushing 32 positioned in the bore Siprovided in the lower right hand corner of the baseS (Fig. 2), and isprovided with a shoulder 35 which slidably engages the head oi therespective `bushing `32. A sprocket 36, made of insulating material,such as Micarta, or the like, is secured on the" upper end of the shalt33 and engages a roller chain belt 31 which in turn meshes with asprocket also made of suitable insulating material. The sprocket 4D issecured on the upper end of a shaft' 4I rotatably mounted in the bushing32 positioned in the bore'il provided in the lower left hand corner ofthe base The shaft 4I is mounted in its respective bushing 32substantially in the same manner as is illustrated in Fig. 2 for theshalt '33 and isl provided with a shoulder which serves 'to maintain thesprocket 40 horizontally aligned with' the sprocket 36 so that the chain31 connecting the two sprockets travels in a horizontal path withrespect to the base 30.

Alternate links of the chain 31 have arms fifi-4;! 'formed integrallytherewith which serve to form a plurality of vertically aligned spacedsupports 'on alternate links throughout the tire length of the chain. Acontact mero. is pivotally mounted between each pair oi.' v .cq/- callyaligned armsM-M by means of a pin positioned in vertically aligned boresprovided in 'ne arms lill- 44. Each contact member IPF- i';

provided with 'a semicircular groove 41 (Figs. 2

and 3) which loosely engages a pin 5l) positioned inanother pair ofvertically aligned bores pro- Pins -50 are designed to engage thesemicircular groove 61 of the members 45-'45 and prevent the membersfrom turning haphazardly about the pin 43 and thereby maintain themembers in a substantially parallelposition with respect to theparticular link on which the member is mounted. At the same time, thepins 5Fl-50 are undersize with re- ,spect to the size of the groove 41so that slight Vmovement of the member' d5 about its respective pin 46is permitted in either direction.

Each of the members 45-45 is provided with a longitudinal semicirculargroove 5I in its outer face, the diameter of which is substantially thesame as the diameter of the average insulating disc I4 positioned on theconductor i2. The members 45-45are'designed so that the somicirculargrooves 5I-5I will engage substantially one-half of the peripheries ofthe discs I4-l4 positioned on the central conductor I 2.

A shaft is provided with a reduced body portion 55 which is rotatablypositioned in the bushing 532 positioned in the bore 3I provided in theupper right hand corner of the base 30 (Fig. 2), and is provided with ashoulder 51 which slidably engages the flanged head of the bushing. Asprocket 60, made of suitable electrical. insu- `lating material, issecured on the upper end of the shaft 55 andengages a roller chain belt5I Which'rneshes with a sprocket 62, likewise made of suitableinsulating material. The sprocket 62 is secured on the end of a shaft 63which has its reduced body portion (not shown) rotatably positioned inthe bushing 32 positioned in the bore 3| provided in the upper left handcorner of the base 30 (Fig. 2). a reduced body portion and a shouldersubstantially the same as that illustrated for the shaft 33, whichshoulder serves to maintain the sprocket 62 in horizontal alignment withthe sprocket 68 mounted on the shaft 55. It will be noted from Fig. 3that the sprockets 66 and 62 which carry the chain 6I are maintained inthe same horizontal plane as the sprockets 36 and 4l) which carry thechain 31, whereby the chains 31 and 6| travel in the same horizontalplane.

The chain 6| is identical in construction with the chain 31 and hascontact members 64-64 mounted on alternate links in the same manner asthat described for the contact members 45--45 mounted on the chain 31.The members 64-64 are identical in construction with the members 45-45,having a longitudinal semicircular groove 65 in the outer face thereofwhich is designed to engage substantially one-half the periphery of theinsulating discs I4-I4, and a'vertical semicircular groove 66 whichloosely engages a pin positioned on the chain 6I in the same manner asdescribed for the chain 31. n

The reduced body portion 34 of the shaft 33 extends beyond the bushing32 and through a bore 61 provided in a partition 69 of the coaxialforming machine II). so as to receive a gear 68 (Fig. 3). The gear 68meshes with a gear 16 secured on the end of the reduced body portion 56of the shaft 55 which extends through a bore 1I provided in thepartition 69 and aligned with the bore 3| provided in the base 30. Thegears 68 and 10 are positioned on the shaft portions 34 and 56 of theshafts 33 and 55, respectively, so that the electrodes 45-45 and 64-64positioned on the adjacent portions of the chains 31 and 6I will line upjuxtaposed with each other in the manner shown in Fig. 2. This geardrive between the shaft 33 and the shaft 55 will main- J tain the chains31 and 6| and the electrodes 45-45 and 64-64, respectively, positivelysynchronized with each other when the electrode I 6 is driven in amanner presently to be described. A worm gear 12 is secured on theextreme end of the body portion 34 of the shaft 33 and engages a worm 13secured on a shaft 14 which is rotatably supported in a suitable manneron the partition 69. A sprocket 15 is secured on the shaft 14 and mesheswith a roller chain belt 1 6 which in turn engages a sprocket (notshown) driven in timed relation with the disc applying apparatus I3 andthe capstan II of the coaxial forming machine Il). The chain 16 and thesprocket 15 are arranged to drive the shaft 14 in a given direction sothat the worm 13 and the worm gear 12 will drive the shaft 33 and itsrespective sprocket 36 in a clockwise direction as indicated by thearrow positioned thereon (Fig. 2).

This direction of rotation of the sprocket 36 serves to advance theinner leg of the chain 31 and the members 45-45 carried thereby fromleft to right, which is the same direction of travel as that in whichthe core I is being advanced from the disc applying apparatus I3 by thecapstan II. The speed ratio between the driven sprocket and its drivingsprocket (not shown) provided on the coaxial forming machine I0 and thespeed ratio between the worm 13 and,

The shaft 63 is provided with' the worm gear 12 is arranged to rotatethe shaft 33 and the sprocket 36 at a speed which will advance the innerleg of the chain 31 and the members 45-45 from left to right at the samerate of speed as that travelled by the core I5.

The gear 68 drives the gear 10 (Fig. 3), the shaft 55 and the sprocket60 secured thereon in a counterclockwise direction which advances theinner leg of the chain 6I and its associated contact members 64-64 fromleft to right in unison with the members 45--45 and the advancing coreI5. A sprocket 11 is provided on the extreme end of the body portion 56of the shaft 55 and meshes with a chain 18, which in turn is connectedto a similar sprocket (not shown) mounted on the testing electrode I1and arranged to drive the testing electrode |1 in the same manner asthat described hereinabove for the testing electrode I6.

In order to maintain the grooves 5| and 65 of the contact members 45-45and Bil-64, respectively, tightly against the periphery of the discsI4-I4 positioned on the advancing conductor I2, there is provided a pairof vertically aligned guides 86 and 8| (Figs. 2 and 3). The guide (shownin detail in Fig. 4) is secured to the base 38 by screws 82-82 and isprovided with a longitudinal groove 83 forming side walls 84-84 whoseends 85--85 curve outwardly and join the sides of the guide 86. Thebottom surface 86 of the groove 83 has its end portions 81-81 adjacentto the curved walls 85-85 tapered downwardly toward the base of theguide 80. The guide 88 is positioned on the base 3D so that thelongitudinal axis of the groove 83 is aligned with the central axis ofthe electrode I6. The width of the groove 83 is such that the innersurface of the walls 84-84 thereof slidably engage an elongated shoulder88 and an elongated shoulder` 90 provided on the lower portion of thecontact members 45-45 and 64-64, respectively, While the depth of thegroove 83 is such that the bottom surface 86 thereof is slidably engagedby the bottom face of the contact members.

The guide 8| is identical in size and shape with the guide 80 but it issecured in an inverted menner above the chains 31 and 6I on a U-shapedsupport 9| (Figs. 2 and 4) which is mounted on the flanged portions ofthe guide 80. The guide 8| also is provided with a longitudinal groove92 having side walls 93-93 whose end portions 94--94 curve outwardly tojoin the sides of the guide 8|. The bottom surface 95 of the groove 92has is end portions, one of which is indicated by the numeral 96,adjacent to the curved walls 94-94 tapered upwardly toward the top ofthe guide 8|. The guide 8| is positioned on the support 9| so that itslongitudinal groove 92 is vertically aligned with the groove 83 of theguide 80. The width of the groove 92 is equal vto the width of thegroove 83, consequently, the

inner surface of the side walls 93-93 thereof slidably engage elongatedshoulders 91 and 98 provided on the -upper portion of the contactmembers 45 and 64, respectively.

The depth of the groove 92 is substantially greater than the depth ofthe groove 83 in order that a pair of elongated leaf springs IDU- |06may be secured to the bottom surface 95 (Fig. 3)

downwardly from the bottom of the groove in the path ofthe'contactmembers advanci'ngthroirgh and since they have only onej endsecured"t'o'the surface 95`the opposite end of'each springisfree toslide on the bottomsurface as ythe 'spring is urged upwardly byengagement with 1the upper face of the contact members 45 and 64,

When the chains 31 and 6I are being driven in a` manner describedhereinabove, each synchronized pair of contact`members45 `and "64 enterthe grooves 83 and 92 of the guides 8|) and 8|, respectively, whereupon'portions `of #their respective shoulders '88, 4SI1, 90 and`598*"slidably engage the inner vside of4 the adjacent curved Walls85-85 and 93-93 of the grooves. As each pair 'of members 45 and |54advance further into the grooves, the entire length of their respectiveshoulders slidably engage the"adjacent sideA walls of the grooves 83andilrespectively, in" which position the walls'serve' to hold thesemic'ii'fcular grooves and E5 of the members k45'and`64, respectively,tightly against the periphery "of a disc I4 engaged thereby. IDD-Iresiliently urge the'contact members and 64 engaged thereby downwardlyin the lgroove 83 of the guide 80 so that the bottoms of the contactmembers make a good physical 'contact with the bottom surface 86 thereofas the contact members are advanced through' the guides 80 and 8|. Theends 85-85 and 96--96`of'the grooves 83 and 92, respectively, aretaperedas described so as to prevent the ends of the contact members 45and 64 from striking the end of f the guide and thereby damaging theContact members or the chains carrying the 'contact members.

Since the discs I4|l 'are'positioned on the conductor I2 at uniformlyspaced intervals by the disc applying apparatus I3, the chains 31 and 6Iare selected to have a pitch Aequaltoene-half the distance between.the-discs I4-I4posit'ioned on the conductor i2.y By'posltioning the'contact members =i5455 and 64,-64 on alternate links of the chains 31and 6I, respectively, having such a pitch it is possible to obtain sucha spacingof the members that each pair of contactmeinbers consisting orone member 45 and one memberf 64 will engage single disc of theadvancing core I5. Since the pitch of the chains 'Sland' 6I is equal toone-half the spacing of the discs on the conductor and since the chainsare'driven in` timed relation with the advancing conductor, no rela--ktive movement occurs between the disc and 'the cont-act members assuccessive pairs of contact members come together andV engage the discson the conductor. The contact members are centrally mounted on theirrespective chain'belts and are or .such length that the ends thereofbutt against the ends of adjacent members When a pair of Contact members'come together in the grooves'33 andQZ yof the guides `80 andl,respectively, the semicircular grooves 5| and65 provided in the contactmembers form a complete circular channel with the exception of a veryslight clearance provided between oppositely disposed contact members.

rherefore, when'two members'come together on the disc I4 of the core I5,practically' theentire periphery ofthe disc is engaged thereby. Thenormal amount of play which existsbetween the contact members andtheirrespectivesupporting links, and between' the iridividuallinksofthe' 'chains makes the contact members some- The leaf springs whatselfadjustable,"tliereby enabling `the testing electrode I6 toengageasubstantial portion of thcperipheryof each disc 'of'the'coaxial unitcore I5, irrespectivelof the fact that the diameter of the discs mayvary slightly. 4Obviously, the chains 31 and *6| `couldbe selected "tohave a pitch equal to vthe 'spacing of the discs on the conductor or`any sub-multiple of the spacing and stillbe operated so that norelative movement occurs betweenthe contactl'm'embers and the discsengaged'thereby.

VThe bared endofl the conductor 26 is secured -Ito-the `support r9| byAa screw IDI and thereby serves toconne'ctthe g`uides180`and 8| directlyto one side-of 'the high potential'burn-out circuit energizedandcontrolled 'by "theelectrical apparatus indicatedg'enerallyat 25.`Byvirtue of the fact that each pairof juxtaposed contact memybers and64 slidably engagethe guides 8U and A8| as they are' advanced bytheir-respectivc'chains 31 and 6| from left to right with the 'advancingcore I5, they are 'in"`turn "charged with the high burn-out-potentiaLinvwhich case the entire portion of the 'core I5` engaged by each pair ofjuxtaposed contactm'embers is thereby subjected tothe burn-outpotential. The high -potential burn-out circuit "is connected directlyto the guidesVA 80 and I so 'that if a 'breakdown should occur at afault present in that portion of the core I5 engagedv by the" severalpairs Aof 'contact members positioned inthe `groove 82 of .the guide"118B, 'the high current owing infthe circuit as a result of thebreakdown is conned tothe 'guide '8G andthe particularpairof electrodesenclos- 'ingthe fault andtherefore is not permitted to travelV throughany portion of' the chains 31 and fSI. The four sprockets-*36,A 40, 60and 62 are `made'of 'suitable insulating material in `order-tocompletely insulate Ithe contact i members rand their respective chainsfrom the" coaxial forming machine because thevforming=machine andtheJcentralconduc'tor `I2 `are' grounded Tat A28, as is the l opposite side1 of i the high potential circuits vconnectedto the electrodesl andfI'I.

machine'of Aknown 'design7 such as the coaxial forming machine indicatedgenerally at I0, so astc engage the discs I4I4of`the core I5 immediatelyafter the-insulating discs have been `placed on the central conductor I2by the disc applying apparatus r I 3. are being driven at the properrate of speed so The chains 31 and 6I asto advance theirrespectivecontact members Afrom leftto'rightat thesame rate of speed asthat at which thecore I5 is being'aclvanced by the capstan "II. Thechainsare synchronized with the movement of the core I5 and' with eachother sothat'each oppositely disposed pair of vcontactmembers'consisting -of"a"contact member 45 and a Contact member 64"ccmecompletely togetherfandsurround aportion of the advancing coreI5"including a portion of the conductor I2 and an individual disc I4positioned thereon as the disc reaches the transverse center line of thesprockets 4an'd'62. Thereafter, the members45 and 64, whichhave been'brought together andinowenclose a portion of thecore I5, travel withlthe conductor and the disc from left to right until thed'isc and thecontact members reach the `transverse centerlinec'f` the sprockets l36and.

Duringthisportion of travel of the conductor and disc,"v the contactmembers slldably engage `the-wal1sH8484`andbottom 86 of' the groove 82provided in the guide 80 and the walls 93-93 and leaf springs IUD- ofthe guide 8|. Since the guide 80 is connected by the conductor 26 to oneside of a highpotential burn-out circuit energized and controlled by theelectrical apparatus indicated generally at 25, the conductor I2 and thediscv I4, being surrounded by the contact members, has the highpotential applied around their respective peripheries, there being anair dielectric surrounding the central conductor I2 (Figs. 2 and'3). Thesprings I IBD-IUE engage the upper surface of the contact members andresiliently urge the bottom surfaces against the bottom 86 of the groove83 thereby providing a good electrical contact between the contactmembers and the guide and preventing any arcing which may occur from aloose contact between the guide and the members.

Should there be afault in the engaged portion of the core I5, such asconductive foreign matter embedded in the disc or metallic sliversattached to the surface of the conductor I2, a path of reduceddielectric strength occurs between the members 45 and 64 and thegrounded central conductor I2. Since the opposite side of the burn-outcircuit is grounded, the burn-out potential breaks down the fault and ahigh current flows therethrough causing the fault to be burned out orvaporized.

It should be noted that the high current caused to flow in the highpotential circuit due to a breakdown of the fault in the core I is notallowed to flow through the links of the chain or through the pins whichpivotally support the contact members 45-45 and 54-64 on theirrespective chains. The current-'flowing through the fault is confinedbetween the members 45 and 64 and the guide 80, thereby preventing anyarcing or pitting to occur between the various moving elements oftheelectrode I6.

As the core I5 and the discs are advanced further toward the right, themembers separate and leave the disc and are carried-around by theirrespective chains until they are again in position to engage anotherportion of the advancing core. It is obvious that no relative movementoccurs between the contact members and the discs engaged thereby, inwhich case the discs cannot in any way be displaced on the cene tralconductor by engagement with the burn-out electrode I6.

Since the discs I4-I 4 positioned on the central conductor I2 are notadvanced through the circular passage formed by the grooves 5I and 65provided on the contact members 45-45 and SII- 64, respectively, theshape of the grooves can be made to conform exactly to the peripheriesof the discs and thereby engage substantially the entire peripherythereof except for the Very small clearance provided between a pair ofoppositely disposed members. Because of this fact, a good mechanicalcontact between the contact members 45-45 and 64-64 and the peripheriesof the discs is obtained, thereby eliminating the possibility of an airgap being present between contacting surfaces of the grooves 5I and 65of the contact members and portions of the peripheries of the discs,which air gap may prevent the contact members from burning out a faultpresent in the advancing core I5. It should also be noted that themembers 45-45 and 64-64 are so designed that when several oppositelydisposed pairs are aligned against the walls 84-84 of the guide 80 andthe walls 93-93 of the guide 8l, the individual contact members of eachchain butt against each other. This ar-l I before the core I5 is engagedby the testing electrode I'I.

After being engaged by the burn-out electrode I6 the advancing core I5is engaged by the testing electrode I'I before being advanced throughthe tube forming die I8. The mechanical construction and operation ofthe testing electrode I'I is identical with that of the burn-outelectrode I6 described hereinabove. However, in its electrical operationthe testing electrode I1 varies from that of the burn-out electrode, inthat the electrode I'I serves to arrest the operation of the coaxialforming machine when a fault is present in the core I5. The electrode IIis connected to one side of a high potential testing circuit energizedand controlled by the electrical apparatus 25, and thereby applies ahigh potential around the peripheries of the insulating discs and thegrounded central conductor. If any faults remain in the core I5 afterbeing engaged by the electrode I6, the high testing potential breaksdown the fault and a high current flows in the circuit. This breakdowncurrent operates current responsive apparatus included in the electrical apparatus 25 to arrest the driving means of the forming machinethereby preventing the defective core I5 from having the tubularconductor 22 formed thereover by the tube forming die While theabove-described electrodes are particularly well adapted to test coaxialunit cores and prevent the machine from forming a defective coaxialunit, they may be modified to test various types of conductors withoutdeparting from the invention, as defined in the annexed claims.

What is claimed is:

1. In an apparatus for electrically testing a continuously advancingcoaxial unit core consisting of a filamentary central conductor havinginsulating discs spacedly positioned thereon including means forgrounding the central conductor and a source of high voltagel animproved electrode for applying a high potential around the advancingcore, which comprises a chain belt having a pair of spaced supportsprovided on alternate links thereof, said chain belt being positioned toone side of the advancing core and having the axis of its path of travelin the same plane with the longitudinal axis of the advancing core, acontact member pivotally mounted between each pair of spaced supportsand having a semicircular groove along the face thereof, a second chainbelt having a pair of spaced supports provided on alternate linksthereof, said second chain being positioned on the opposite side of theadvancing core and having the axis of its path of travel in the sameplane with that of the first-mentioned chain belt, a contact memberpivotally mounted between each pair of spaced supports of said secondchain belt and having a semicircular groove along the face thereof,means for driving said first and second chain belts in unison so as toadvance the contact members on the adjacent legs thereof in the samedirection and at the same rate of speed as that travelled by theadvancing core for a predetermined portion of their travel, said chainbelts being synchronized so that the contact members on the adjacentlegs of the chain belts are juxtaposed during their period of travelwith the core unit and so spaced. that the contactvl members on the.adjacent legs thereof enclose a.

portion of the. core advancingv therebetween, and upper and lower guidesfor holding each pair of advancing juXtaposedcontact members togetherduring their travel with the core so that their. respective semicirculargroovesA engage the periphery of the discs of the core. unit.

2. In an apparatus for electrically testing a -continuously advancingcoaX-ial unit. core consisting of alamentary central. conductor havinginsulating discs spacedlyv positionedgthereon including means for`grounding the. centralconductors and a source of high-voltage, animproved electrode for applying a high Potential aroundlthe advancingcore,. which comprises a chain. belt having a pair of spaced. supportsVprovided on. alternate links thereof., said. chainbeltbeing positionedto one side of the advancing core andthe axis of its pathA of. travel inthe same plane with` the longitudinal axis of the.core,.a-contact mem.-vber pivotally mounted between each pair of spaced supports andhavingasemicircular groove.

along4 the face thereof, a. secondchain. belthaving a pair of'spaced.supports provided` on.. alternate links thereof, said second chain.being` positioned on the opposite sideof the.. advancing core and havingthe axis of its. pathof travel. in the same plane with thatof therst-rnentionedlchain belt, an elongated contact.v member pivotallymounted between each. pair of spaced supports ot said second chain beltand havingasemicircular groove along the face thereof adjacent to thecoreA unit, means for driving said rst and second chain belts so as toadvance. their respective contact members in the same directionas and atthe same.

linear speed as that travelled by the advancing core for a predeterminedportion of vtheir traveL,

means for synchronizing the movement of the chain belts so that thecontact members of. each4 ing: of` a nlamentar-yrcentrmconductor havinginsulating, discs' spa'cedlyr positioned thereon includinga. highvoltage. testingl circuit and means i'or connecting the, centralconductor to one side thereof, `an improvedeleotrode for applying a highpotential. aroundtheadvancing core, which comprises a-pair of endlesschain belts spaced equidistantly astride the path` of travel of theadvancing core and having the axis of their respective paths oftraveleligned with the longitudinal axisofthecore, a.` plurality of."contact members mounted on. each chainbelt and having a semicirculargroovetherein for engagingI the peripheries of the discspositioned on:said advancing core, means' for. driving, the. chain belts so that theadjacent legs/travel inthe same direction and at-thesamelinearv speed asthat oiY the advancing core, means for synchronizing` the-movement ofsaid chain.belts.witht respect toseach other so that thefcontactmemberson the adjacent legs of the chain belts are juxtaposed; during, theirperiod of travel with the advancing, core, saidI chain belts beingsospaced with respect to the core advancing. between. said. adjacentlegs, upper and lower guides arranged to hold the contact: membersagainst the discs onq the advancing conductor for. a predeterminedlength of travel. of the contact-members, resilient-means provided onthe upper guide member for urging thecontact members downwardly sothatthey makea. good sliding contact with the lowerv guide therewith,and means for electrically insulating` the chain belt synchronizingmeans. and .driving means from the track members, wherebywhen one sideof asource of potential is connected tothe lower track member thecontact members engaged thereby are raisedr teva. valueoi potentialsubstantially above that of the central conductor of the advancing core.

DAWSON4 M. TAGGART.

REFERENCES. CITED The following references are of record i'n the file ofthis patent:

UNITED STATES IATENTS Number Name Date 1,247,501 Butcher Nov. 20, 19171,288,866 Friel Dec. 28, 1918 1,361,970 Dickey Dec. 14,1920 2,092,487Weston Septl 7, 1937 2,386,127 Longfellow Oct. 2, 1945

